A. Field of the Invention
This invention relates to the preparation of sulfones and compounds containing carbon chains having conjugated unsaturation and more particularly relates to the preparation of such sulfones which contain halogen groups which can be eliminated in conjunction with hydrogen and SO.sub.2 to yield a carbon chain having conjugated unsaturation.
B. History of the Prior Art
In the prior art, some compounds containing conjugated nonaromatic aliphatic unsaturated carbon-carbon bonds were readily prepared from petroleum feed stock. Unfortunately, only short chain compounds containing such conjugated bonds could be prepared in this way and more complex compounds were difficult to prepare or had not been prepared at all. Such compounds containing conjugated unsaturation are highly desirable for numerous reasons. In particular, such compounds can act as monomers for the preparation of polymeric materials having special properties, have utility in the manufacture of fragrances and as intermediates in the manufacture of numerous products such as fungicides, algicides, insect sex attractants and other biologically active compounds.
It has been known that certain aliphatically unsaturated compounds could be prepared by means of a reaction known as the Ramberg-Backlund reaction. In this reaction, a haloalkyl sulfone yields an olefin upon treatment with a base. Unfortunately, such haloalkyl sulfones have been difficult to prepare and, in general, do not yield compounds containing conjugated aliphatic unsaturation. Descriptions of the Ramberg-Backlund Reaction and some of the difficult methods for preparation of the intermediate sulfones are discussed in "The Ramberg-Backlund Rearrangement", Paquette, Organic Reactions, Vol. 25, Wiley & Sons (1977); "The Base-Induced Rearrangement of Alphahalosulfones"; Paquette; "Accounts of Chemical Research", Vol. 1, p. 209 (1968); "Reactions of Organosulfur Compounds", Eric Block, pp. 75-79, Academic Press (1978); "The Michael Induced Ramberg-Backlund Olefin Synthesis", Chen et al, Tetrahedron Letters, Issue 51, pp. 4527 (1977) and "The Michael Induced Ramberg-Backlund Homologation to Conjugated Isoprenoids", Berger et al, Tetrahedron, Vol. 37, pp. 417-424, (1981); and "A Novel Synthesis of Linear Polyenes via Conjugate Addition of Cuprates to Alpha, Beta, Gamma, Delta Di-unsaturated Sulfones followed by SO.sub.2 Extrusion", Naff et al, Tetrahedron, Vol. 23, No. 48, pp. 5043-5046 (1982).
The primary problem in the prior art, with using the Ramberg-Backlund Reaction to obtain conjugated olefins, has been the preparation of appropriate sulfones which lend themselves to preparation of conjugated compounds. In the prior art, there has been no good single-step process for the preparation of such sulfones.
Examples of prior art references which deal with the preparation of sulfones which are subsequently treated to obtain some unsaturation but which unfortunately did not yield aliphatic conjugated unsaturation, are U.S. Pat. Nos. 3,830,862 and 4,022,804. U.S. Pat. No. 4,022,804 is particularly interesting since in one example chloromethyl sulfonic acid bromide is reacted with 2,5-dihydrofuran in the presence of a peroxide and then triethylamine to form 3-chloromethylsulfonyl 2,5-dihydrofuran. While the preparation of this particular sulfone is interesting, the resulting compound is unable to yield an aliphatic conjugated diene upon elimination of the halogen and sulfonyl group.
Often the preparation of such sulfones in the prior art required reaction temperatures in excess of 25.degree. C. or else required exceedingly long reaction times, e.g. in excess of 15 hours. An exception to the elevated temperature or extended reaction time is provided by Example 9 of U.S. Pat. No. 4,022,804 which does, however, in accordance with the teachings of the patent require peroxide catalyst and which results in a sulfone which cannot yield a non-aromatic conjugated diene.